1. Field of the Invention
This invention relates to a process for the production of C.sub.2 to C.sub.6 alcohols, particularly isopropanol, by the hydration of C.sub.2 to C.sub.6 olefins, for example, propylene, in the presence of an acidic ion exchange resin as a hydration catalyst, and for the recovery of C.sub.2 to C.sub.6 alcohols from the reaction product.
2. Description of the Prior Art
Isopropanol was the first petrochemical made in the United States and has been commercially available since 1920. Previously, isopropanol was produced by the indirect hydration of propylene. This was accomplished by esterification of propylene with sulfuric acid and the subsequent hydrolysis of the ester to the alcohol and sulfuric acid. This process, however, requires reconcentration of the sulfuric acid, leads to corrosion of apparatus, high heat requirements and pollution, all of which dictate the need for development of direct hydration routes to produce alcohols from olefins.
More recently, three processes have been developed to catalytically hydrate olefins to alcohols, namely, gas phase hydration of olefins using a fixed-bed catalyst consisting of a supported phosphoric acid, coexisting gas-liquid phase hydration of olefins in the presence of a cation-exchange resin, and liquid-phase hydration of an olefin in the presence of a dissolved tungsten catalyst.
It has been demonstrated that alcohol formation, in an olefin hydration reaction, is generally favored by low temperatures and high pressures, since the reaction equilibrium of olefin to alcohol is satisfactory at these conditions. Thus, a mechanism to control the reaction temperature of an olefin hydration reaction is highly beneficial in a process for producing alcohols.
The hydration of olefins to alcohols in the presence of a catalyst is known and appreciated by the prior art. For example, U.S. Pat. No. 3,994,983, issued Nov. 30, 1976, relates to a process for the production of C.sub.2 to C.sub.6 alcohols by hydration of olefins in the presence of water and an acidic cation exchange resin catalyst. In particular, vaporous lower aliphatic olefins containing from 2 to 6 carbon atoms are contacted with water in the liquid phase in the presence of acids or strongly acidic solids at elevated temperature and pressure.
U.S. Pat. No. 3,955,939 issued May 11, 1976 discloses a process for recovering a water-free mixture of isopropyl alcohol, diisopropyl ether, and by products consisting of n-propanol, acetone, hexanol, etc. from the catalytic hydration of propylene in the gaseous phase. The product from the hydration reaction is separated from water utilizing diisopropyl ether produced in the process. The water-free mixture thus formed is used as an additive for gasoline.
Another process for producing isopropanol and blending the same with gasoline is disclosed in U.S. Pat. No. 3,455,664 issued July 15, 1969. Propylene is hydrated with water to isopropyl alcohol at increased temperature and pressure in the presence of a catalyst consisting, for example, of a polystyrene divinyl benzene sulfonic acid resin. Other suitable catalysts include silica-alumina, acidic clays, reduced tungsten oxides, etc. The isopropyl alcohol thus produced is extracted with a gasoline reformate and blended with gasoline.
U.S. Pat. No. 3,988,381, issued Oct. 26, 1976 discloses a hydration method and catalyst for producing isopropanol. The catalyst is a crosslinked copolymer produced by polymerizing diethylvinyl-phosphonate and divinylsulfone in the presence of a radical initiator, i.e., azoisobutyronitrile under a nitrogen atmosphere. Isopropanol is produced by hydrating propylene with water in contact with the above crosslinked copolymer.
U.S. Pat. No. 3,548,013, issued Dec. 15, 1970 discloses a process for the production of C.sub.3 to C.sub.6 alcohols from the corresponding olefins, wherein a C.sub.3 to C.sub.6 olefins is hydrated to an alcohol with water in the presence of a hydration catalyst, for example, a polystyrene divinyl benzene sulfonic acid resin. The alcohol produced in the process is separated from the reaction mixture by flash distillation.
As can readily be determined from the above, there is an ongoing research effort to provide new and improved methods for producing alcohols from olefins using indirect as well as direct hydration catalysts.
Accordingly, it is an object of this invention to provide a process for the direct hydration of C.sub.2 to C.sub.6 olefins to alcohols.
Another object of this invention is to provide a hydration process for producing an alcohol wherein said alcohol is counter currently extracted with a solvent to provide an economical method of separating the alcohol from water in the process.
These and other objects of the invention will be apparent to those skilled in the art from the following description in conjunction with the drawings.